This invention relates to polyimidesiloxanes having a high T.sub.g and a relatively low bonding temperature and to hot melt adhesives made therefrom, particularly in the form of tapes. In particular, it relates to polyimidesiloxanes made by reacting 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) or bis(3,4-dicarboxyphenyl)ether dianhydride, also known as oxydiphthalic anhydride (ODPA), with a siloxane-containing diamine and a mixture of at least two of the following diamines: 2,2-bis(4[4-aminophenoxy]phenyl)propane (BAPP), 2,2'-bis(4-aminophenyl)-1,4-diisopropylbenzene, also known as bis-aniline P (BAP), 3,3'-diaminophenylsulfone (APS), and 1,3'-bis(3-aminophenoxy)benzene (APB).
In the electronics industry, adhesive tapes are used for a variety of purposes such as, for example, bonding a metal lead frame to an integrated circuit chip. Such tapes, useful for LOC (lead on chip) attachments, are required to be of high purity, have excellent adhesive properties, and be easy to apply using mass production techniques.
In some of these applications, it is very desirable for the adhesive tape to have a T.sub.g in excess of about 200.degree. C. so that a chip bonded with the adhesive tape remains rigid during wire bonding, as rigidity prevents the formation of weak bonds. At the same time, the temperature at which the tape bonds to a substrate should be relatively low to permit more rapid processing of the chips and cause less thermal stress and damage. (See U.S. Pat. No. 4,624,978.)
Normally, the requirements for a high T.sub.g and a relatively low bonding temperature are contradictory. That is, most polyimidesiloxanes have a bonding temperature at least 100.degree. C. higher than their T.sub.g, and the higher the T.sub.g the greater will usually be the difference between the bonding temperature and the T.sub.g.